Polycarbonate diol having high proportion of primary terminal OH

ABSTRACT

Disclosed is a polycarbonate diol having diol monomer units and carbonate monomer units, wherein the amount of at least one diol monomer unit selected from the group consisting of a 1,5-pentanediol unit and a 1,6-hexanediol unit is from 50 to 100% by mole, based on the total molar amount of the diol monomer units, and wherein the ratio of primary hydroxyl groups in all terminal groups of the polycarbonate diol is in a specific range. Also disclosed is a thermoplastic polyurethane obtained by copolymerizing the above-mentioned polycarbonate diol and a polyisocyanate.

This application is the national phase under 35 U.S.C. § 371 of PCTInternational Application No. PCT/JP01/04373 which has an Internationalfiling date of May 24, 2001, which designated the United States ofAmerica.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a polycarbonate diol having anextremely high ratio of primary hydroxyl groups in all terminal groups.More particularly, the present invention is concerned with apolycarbonate diol having diol monomer units and carbonate monomerunits, wherein the amount of at least one diol monomer unit selectedfrom the group consisting of a 1,5-pentanediol unit and a 1,6-hexanediolunit is from 50 to 100% by mole, based on the total molar amount of thediol monomer units, and wherein the ratio of primary hydroxyl groups inall terminal groups of the polycarbonate diol is in an extremely high,specific range and, therefore, the ratio of secondary terminal hydroxylgroups is extremely low. The present invention is also concerned with athermoplastic polyurethane obtained by copolymerizing theabove-mentioned polycarbonate diol and an organic polyisocyanate.

When the polycarbonate diol of the present invention is used forproducing a thermoplastic polyurethane, a polyester elastomer and thelike, the desired polymerization reactions can proceed at high rate, ascompared to the case of the use of the conventional polycarbonate diol.Further, the thermoplastic polyurethane of the present invention hasremarkably excellent properties with respect to strength, elongation,impact resilience and low temperature properties, as compared to theproperties of a thermoplastic polyurethane obtained using theconventional polycarbonate diol.

2. Prior Art

A polyurethane and a urethane-, ester- or amide-based thermoplasticelastomer are used in the art. The soft segments of the polyurethane andthermoplastic elastomer are composed of structural units formed from apolyester polyol and/or a polyether polyol, each of which has a hydroxylgroup at each of the molecular terminals thereof (for example, U.S. Pat.Nos. 4,362,825 and 4,129,715). A polyester polyol, such as a polyadipatepolyol, has poor hydrolysis resistance. Due to the poor hydrolysisresistance, for example, a polyurethane containing, as soft segments,structural units formed from a polyester polyol has a disadvantage inthat cracks are likely to occur and mold is likely to grow on thesurface of the polyurethane within a relatively short period of time.Therefore, the use of such a polyurethane is considerably limited. Onthe other hand, a polyurethane containing, as soft segments, structuralunits formed from a polyether polyol has good hydrolysis resistance.However, the polyurethane has a disadvantage in that it has poorresistance to light and oxidative degradation. The disadvantages ofthese polyurethanes are, respectively, attributed to the presence ofester groups in the polymer chain and the presence of ether groups inthe polymer chain.

A polycarbonate polyol prepared from 1,6-hexanediol is sold as a polyolusable for forming soft segments which have excellent resistance tohydrolysis, light, oxidative degradation, heat and the like. Thisresistance is due to the fact that carbonate linkages in the polymerchain exhibit extremely high chemical stability.

In recent years, a thermoplastic polyurethane which is produced using,as a soft segment, a copolycarbonate diol prepared from a mixture of1,6-hexanediol and 1,4-butanediol or 1,5-pentanediol is attractingattention because of its great advantages. (The above-mentionedcopolycarbonate diol is disclosed in Examined Japanese PatentApplication Publication No. Hei 5-029648 (corresponding to EP 302712 andU.S. Pat. Nos. 4,855,377 and 5,070,173) and Unexamined Japanese PatentApplication Laid-Open Specification No. Hei 5-25264; and theabove-mentioned thermoplastic polyurethane is disclosed in UnexaminedJapanese Patent Application Laid-Open Specification No. Hei 5-51428 andJapanese Patent Publication No. 1985394 (corresponding to EP 302712 andU.S. Pat. Nos. 4,855,377 and 5,070,173).) Specifically, suchthermoplastic polyurethane has advantages not only in that it hasremarkably excellent properties with respect to flexibility, lowtemperature properties and elastic recovery, as well as the sameexcellent properties as mentioned above and as achieved by using, as asoft segment, a polycarbonate diol prepared from 1,6-hexanediol, butalso in that the thermoplastic polyurethane can be easily spun toproduce a polyurethane fiber.

A polycarbonate diol is produced by effecting a transesterificationreaction between a diol monomer having two primary hydroxyl groups andan organic carbonate compound, such as ethylene carbonate, dimethylcarbonate, diethyl carbonate or diphenyl carbonate, in the presence orabsence of a transesterification catalyst.

The prior art document disclosing a copolycarbonate diol prepared from amixture of 1,6-hexanediol and 1,4-butanediol (Unexamined Japanese PatentApplication Laid-Open Specification No. Hei 5-25264) describes that analiphatic polycarbonate diol containing 60 to 90% by mole of recurringunits formed from 1,4-butanediol, based on the total molar amount of thediol monomer units, exhibits a stable reactivity in a reaction thereofwith a polyisocyanate for forming a polyurethane.

On the other hand, however, in the course of the studies of the presentinventors, it was found that an aliphatic polycarbonate diol, obtainedby the method of Unexamined Japanese Patent Application Laid-OpenSpecification No. Hei 5-029648, specifically an aliphatic polycarbonatediol containing 50% by mole or more of a recurring unit selected fromthe group consisting of a 1,5-pentanediol unit and a 1,6-hexanediolunit, based on the total molar amount of the diol monomer units, has thefollowing problems. When a polyurethane-forming reaction is conductedusing such an aliphatic polycarbonate diol, not only does thepolymerization reaction rate become low, but also the resultantthermoplastic polyurethane has poor properties with respect to strength,elongation, impact resilience, low temperature properties and the like.Further, when the above-mentioned aliphatic polycarbonate diol is usedfor the production of a polyester elastomer, the polymerization reactionrate becomes low.

SUMMARY OF THE INVENTION

In this situation, the present inventors have made extensive andintensive studies with a view toward elucidating the reason why asatisfactory polymerization reaction rate cannot be obtained when aconventional polycarbonate diol is used for the production of apolyurethane or a polyester elastomer. As a result, it has unexpectedlybeen found that a polycarbonate diol contains secondary terminalhydroxyl groups derived from impurity monomers although the amount ofthese hydroxyl groups is very small, and such secondary terminalhydroxyl groups, even if the amount thereof is very small, cause alowering of the reactivity of the polycarbonate diol during apolyurethane-forming reaction and a polyester-forming reaction. Further,the present inventors have found that the problems of the prior art canbe solved by a polycarbonate diol having diol monomer units andcarbonate monomer units, wherein the amount of at least one diol monomerunit selected from the group consisting of a 1,5-pentanediol unit and a1,6-hexanediol unit is from 50 to 100% by mole, based on the total molaramount of the diol monomer units, and wherein the ratio of primaryhydroxyl groups in all terminal groups of the polycarbonate diol is inan extremely high, specific range and, therefore, the ratio of secondaryterminal hydroxyl groups is extremely low to an extent which has notever been achieved. Specifically, the present inventors have found thatsuch a polycarbonate diol having an extremely high ratio of primaryterminal hydroxyl groups exhibits high reactivity in apolyurethane-forming reaction and a polyester-forming reaction, therebyachieving high polymerization reaction rate. Also, the present inventorshave found that, when such a polycarbonate diol having an extremely highratio of primary terminal hydroxyl groups is used as a raw material forproducing a thermoplastic polyurethane, advantages are achieved not onlyin that the desired polymerization reactions can proceed at high rate,but also in that the produced thermoplastic polyurethane has remarkablyexcellent properties with respect to strength, elongation, impactresilience and low temperature properties. The present invention hasbeen completed based on these novel findings.

Accordingly, it is an object of the present invention to provide apolycarbonate diol exhibiting excellent polymerization activity in areaction for producing a polyurethane and a reaction for producing apolyester elastomer.

It is another object of the present invention to provide a thermoplasticpolyurethane obtained by copolymerizing the above-mentionedpolycarbonate diol and a polyisocyanate, wherein the thermoplasticpolyurethane can be used as various materials having excellentproperties with respect to flexibility, heat resistance, low temperatureproperties, weathering resistance, strength, and molding processability.

The foregoing and other objects, features and advantages of the presentinvention will be apparent to those skilled in the art from thefollowing detailed description and appended claims.

DETAILED DESCRIPTION OF THE INVENTION

In one aspect of the present invention, there is provided apolycarbonate diol comprising recurring units each independentlyrepresented by the following formula (1):

-   -   wherein R represents a divalent aliphatic or alicyclic        hydrocarbon group having 2 to 10 carbon atoms,        and terminal hydroxyl groups,

wherein 50 to 100% by mole of the recurring units of formula (1) areeach independently represented by the following formula (2):

wherein n is 5 or 6, and

wherein:

when the amount of recurring units of formula (2) wherein n=5 is from 50to 100% by mole, based on the total molar amount of the recurring unitsof formula (1), the polycarbonate diol has a primary terminal OH ratioof 97% or more, and

when the amount of recurring units of formula (2) wherein n=5 is from 0to less than 50% by mole, based on the total molar amount of therecurring units of formula (1), the polycarbonate diol has a primaryterminal OH ratio of 99% or more,

the primary terminal OH ratio being defined as the weight percentage ofdiol monomers having primary hydroxyl groups at both terminals thereof,based on the total weight of the alcohols inclusive of diol monomers,wherein the alcohols, inclusive of diol monomers, are derived from theterminal diol segments of the polycarbonate diol and contained in afraction obtained by heating the polycarbonate diol at a temperature offrom 160 to 200° C. under a pressure of 0.4 kPa or less while stirring.

For easy understanding of the present invention, the essential featuresand various preferred embodiments of the present invention areenumerated below.1. A polycarbonate diol comprising recurring units each independentlyrepresented by the following formula (1):

wherein R represents a divalent aliphatic or alicyclic hydrocarbon grouphaving 2 to 10 carbon atoms,

and terminal hydroxyl groups,

wherein 50 to 100% by mole of the recurring units of formula (1) areeach independently represented by the following formula (2):

wherein n is 5 or 6, and

wherein:

when the amount of recurring units of formula (2) wherein n=5 is from 50to 100% by mole, based on the total molar amount of the recurring unitsof formula (1), the polycarbonate diol has a primary terminal OH ratioof 97% or more, and

when the amount of recurring units of formula (2) wherein n=5 is from 0to less than 50% by mole, based on the total molar amount of therecurring units of formula (1), the polycarbonate diol has a primaryterminal OH ratio of 99% or more,

the primary terminal OH ratio being defined as the weight percentage ofdiol monomers having primary hydroxyl groups at both terminals thereof,based on the total weight of the alcohols inclusive of diol monomers,wherein the alcohols, inclusive of diol monomers, are derived from theterminal diol segments of the polycarbonate diol and contained in afraction obtained by heating the polycarbonate diol at a temperature offrom 160 to 200° C. under a pressure of 0.4 kPa or less while stirring.

2. A polycarbonate diol according to item 1 above, wherein, when thepolycarbonate diol is decomposed with an alkali to obtain a mixture ofdiol monomers corresponding to all of the diol segments of thepolycarbonate diol, the mixture of diol monomers exhibits:

a primary hydroxyl terminal purity of 99.0% by weight or more when, inthe polycarbonate diol, the amount of recurring units of formula (2)wherein n=5 is from 50 to 100% by mole, based on the total molar amountof the recurring units of formula (1), and

a primary hydroxyl terminal purity of 99.5% by weight or more when, inthe polycarbonate diol, the amount of recurring units of formula (2)wherein n=5 is from 0 to less than 50% by mole, based on the total molaramount of the recurring units of formula (1),

the primary hydroxyl terminal purity being defined as the weightpercentage of the diol monomers having primary hydroxyl groups at bothterminals thereof, based on the weight of the mixture of diol monomers.

3. A thermoplastic polyurethane obtained by copolymerizing thepolycarbonate diol of item 1 or 2 above and a polyisocyanate.

Hereinbelow, the present invention will be described in detail.

The polycarbonate diol of the present invention is a polycarbonate diolin which at least one diol monomer unit selected from the groupconsisting of a 1,5-pentanediol unit and a 1,6-hexanediol unit ispresent in an amount of 50 to 100% by mole, based on the total molaramount of the diol monomer units, wherein, when the amount of the1,5-pentanediol units is from 50 to 100% by mole, the polycarbonate diolhas a primary terminal OH ratio of 97% or more, preferably 99% or more,and when the amount of the 1,5-pentanediol units is from 0 to less than50% by mole, the polycarbonate diol has a primary terminal OH ratio of99% or more, preferably 99.4% or more, more preferably 99.6% or more. Asa result of the extensive and intensive studies of the presentinventors, it has been found that the above-mentioned polycarbonate diolof the present invention exhibits excellent polymerization activity andhigh polymerization reaction rate during a polyurethane-forming reactionand hence can be suitably used as a raw material for producing apolyurethane. Further, it has been found that the above-mentionedpolycarbonate diol also exhibits excellent polymerization activity andhigh polymerization reaction rate during a reaction for producing apolyester elastomer.

When the primary terminal OH ratio of the polycarbonate diol is smallerthan the above-mentioned range required in the present invention, aproblem arises in that, when the polycarbonate diol is reacted with apolyisocyanate in order to produce a thermoplastic polyurethane, thepolymerization reaction rate becomes markedly lowered (see Examples 5 to10 and Comparative Examples 5 to 10, and Examples 11 to 13 andComparative Examples 11 to 13, which are described below). It ispresumed that the reason for the above-mentioned lowering of thepolymerization reaction rate resides in that the secondary terminalhydroxyl groups have a steric hindrance, which will lower theirreactivity to isocyanate groups. It should be noted that, when apolyurethane-forming reaction between such a polycarbonate diol (whichdoes not satisfy the primary terminal OH ratio requirement of thepresent invention) and a polyisocyanate is conducted for a long periodof time in order to compensate for the lowering of the polymerizationreaction rate, the produced thermoplastic polyurethane exhibits poormechanical properties (that is, a lowering of tensile strength,elongation and impact resilience occurs) (see Examples 5, 7 and 8 andComparative Examples 11 to 13, which are described below). The reasonfor the lowering of the mechanical properties of the polyurethaneproduced is considered to reside in that, due to the presence ofpolycarbonate diol chains having secondary hydroxyl terminals (whichexhibit low reactivity to isocyanate groups), during a long reactiontime, the molecular weight distribution (Mw/Mn) of the polyurethanebeing produced becomes too broad, and also the ratio of low molecularweight polyurethane molecules becomes large.

In the present invention, it is preferred that the primary terminal OHratio is as high as possible, because the polymerization activity of thepolycarbonate diol is increased in accordance with an increase in theprimary terminal OH ratio of the polycarbonate diol. For infinitelyincreasing the primary terminal OH ratio of the polycarbonate diol, itis necessary to infinitely increase the purity of 1,5-pentanediol and/or1,6-hexanediol, so that too large an amount of labor will be necessaryfor the purification. However, the excellent effects of the presentinvention can be obtained as long as the primary terminal OH ratio ofthe polycarbonate diol is not lower than the lower limit of theabove-mentioned range required in the present invention. Therefore,there is no necessity for increasing the primary terminal OH ratio to alevel infinitely higher than the lower limit of the above-mentionedrange required in the present invention.

The primary terminal OH ratio referred to in the present invention isdefined as the weight percentage of diol monomers having primaryhydroxyl groups at both terminals thereof, based on the total weight ofthe alcohols, inclusive of diol monomers, wherein the alcohols,inclusive of diol monomers, are derived from the terminal diol segmentsof the polycarbonate diol and contained in a fraction obtained byheating the polycarbonate diol at a temperature of from 160 to 200° C.under a pressure of 0.4 kPa or less while stirring.

Specifically, a polycarbonate diol (in an amount of from 70 g to 100 g)is heated at a temperature of from 160 to 200° C. under a pressure of0.4 kPa or less while stirring to thereby obtain a fraction in an amountwhich is approximately 1 to 2% by weight of the polycarbonate diol. Thatis, approximately 1 g (0.7 to 2 g) of a fraction is obtained, and theobtained fraction is recovered using approximately 100 g (95 g to 105 g)of ethanol as a solvent, thereby obtaining a sample solution. Theobtained sample solution is analyzed by gas chromatography (GC) tothereby obtain a chromatogram, and the primary terminal OH ratio iscalculated from the peak areas in accordance with the following formula:Primary terminal OH ratio (%)=(sum of the areas of the peaks ascribed todiol monomers having primary hydroxyl groups at both terminalsthereof)÷(sum of the areas of the peaks ascribed to the alcoholsinclusive of diol monomers (but exclusive of ethanol))×100.

Specific examples of “alcohols inclusive of diol monomers (but exclusiveof ethanol)” which are detected by the GC analysis performed fordetermining the primary terminal OH ratio include 1,4-butanediol,1,5-pentanediol, 1,6-hexanediol, 1,5-hexanediol, 1,4-cyclohexanediol,1,4-pentanediol, 1-butanol, 1-pentanol, 1-hexanol and the like. A diolmonomer, such as 1,5-pentanediol or 1,6-hexanediol, used for producingthe polycarbonate diol of the present invention, is purified bydistillation in the production thereof, but an impurity alcohol having aboiling point which is close to that of the diol monomer to be purifiedwill remain in the diol monomer. However, since the boiling point ofethanol is much lower than that of a diol monomer to be purified, evenwhen ethanol is contained in a diol monomer to be purified, ethanol willbe removed from the diol monomer by the above-mentioned distillationpurification. Therefore, all of ethanol contained in the sample solutionwhich is subjected to GC for determining the primary terminal OH ratiois ascribed to the ethanol used for recovering the fraction.

The primary terminal OH ratio is the ratio of the primary terminal OHgroups in all terminal groups of the polycarbonate diol. When apolycarbonate diol is heated under the above-mentioned conditions,namely at a temperature of from 160 to 200° C. under a pressure of 0.4kPa or less while stirring, only the terminal portions of thepolycarbonate diol are decomposed to form diol monomers, and the diolmonomers are distilled off and recovered as a fraction. The primaryterminal OH ratio is the weight percentage of diol monomers havingprimary hydroxyl groups at both terminals thereof, based on the totalweight of all alcohols. The higher the primary terminal OH ratio, thehigher the polymerization activity of the polycarbonate diol during apolyurethane-forming reaction and a polyester-forming reaction.

In the present invention, the lower limit of the primary terminal OHratio is different depending on whether the amount of recurring units offormula (2) wherein n=5 (that is, 1,5-pentanediol-derived units) is from50 to 100% by mole or is from 0 to less than 50% by mole. The reason forthis is as follows. 1,5-Pentanediol and/or 1,6-hexanediol are/is used asa raw material for producing the polycarbonate diol of the presentinvention. Among the impurities contained in 1,6-hexanediol, an impuritycontaining a secondary OH group is 1,4-cyclohexanediol, and both of thetwo OH groups of 1,4-cyclohexanediol are secondary OH groups. On theother hand, among the impurities contained in 1,5-pentanediol,impurities containing a secondary OH group are 1,5-hexanediol and1,4-cyclohexanediol. As mentioned above, both of the two OH groups of1,4-cyclohexanediol are secondary OH groups. However, with respect to1,5-hexanediol, one of the two OH groups thereof is a secondary OHgroup, but the other OH group thereof is a primary OH group. Therefore,when the secondary OH group of a 1,5-hexanediol molecule (an impurity)binds to a carbonate compound during the transesterification reactionfor producing a polycarbonate diol, there is a possibility that theprimary OH group of the 1,5-hexanediol molecule becomes the primaryterminal OH group of the final polycarbonate diol. In such case, noproblems will be caused by the 1,5-hexanediol molecule. The primaryterminal OH ratio is an index for evaluating the ratio of diol monomerunits formed from diol monomers having primary OH groups at bothterminals thereof in all of the diol monomer units constituting theterminal portions of the polycarbonate diol, and hence the primaryterminal OH ratio cannot be increased by the presence of 1,5-hexanediol,which has a primary terminal OH group at only one terminal thereof.Thus, when the amount of 1,5-pentanediol-derived units (1,5-pentanediolmonomer units) is from 50 to 100% by mole (that is, when the ratio of1,5-hexanediol in the impurities contained in the raw materials ishigh), due to the presence of 1,5-hexanediol, the actual primaryterminal OH ratio of the polycarbonate diol is considered to becomeslightly higher than that determined by the above-mentioned method.Accordingly, when the amount of 1,5-pentanediol-derived units(1,5-pentanediol monomer units) is from 50 to 100% by mole, the lowerlimit of the primary terminal OH ratio defined in the present inventioncan be slightly lower than that in the case where the amount of1,5-pentanediol-derived units (1,5-pentanediol monomer units) is from 0to less than 50% by mole. Based on this finding, in the presentinvention, the lower limit of the primary terminal OH ratio is differentas between the case where the amount of 1,5-pentanediol-derived units(1,5-pentanediol monomer units) is from 50 to 100% by mole and the casewhere the amount of 1,5-pentanediol-derived units (1,5-pentanediolmonomer units) is from 0 to less than 50% by mole.

As explained above, the primary terminal OH ratio is the ratio of theprimary OH groups in all terminal groups of the polycarbonate diol. Onthe other hand, the composition of all diol segments constituting thepolycarbonate diol can also be analyzed. This analysis can be made by amethod in which the polycarbonate diol is decomposed with an alkali toobtain a mixture of diol monomers corresponding to all of the diolsegments of the polycarbonate diol, and the obtained mixture is analyzedto determine the composition of all diol segments of the polycarbonatediol. Thus, a primary hydroxyl terminal purity can be determined,wherein the primary hydroxyl terminal purity is defined as the weightpercentage of the diol monomers having primary hydroxyl groups at bothterminals thereof, based on the weight of the mixture of diol monomers.It is preferred that the polycarbonate diol of the present inventionexhibits a primary hydroxyl terminal purity of 99.0% by weight or morewhen the amount of 1,5-pentanediol units in the polycarbonate diol isfrom 50 to 100% by mole, based on the total molar amount of the diolmonomer units. In this case, it is more preferred that the primaryhydroxyl terminal purity is 99.2% by weight or more, more advantageously99.5% by weight or more. On the other hand, it is preferred that thepolycarbonate diol of the present invention exhibits a primary hydroxylterminal purity of 99.5% by weight or more when the amount of1,5-pentanediol units in the polycarbonate diol is from 0 to less than50% by mole, based on the total molar amount of the diol monomer units.In this case, it is more preferred that the primary hydroxyl terminalpurity is 99.7% by weight or more.

Exemplified below is a specific method in which a polycarbonate diol isdecomposed with an alkali to obtain a diol monomer mixture, followed byanalysis of the diol composition thereof (that is, followed bydetermination of a primary hydroxyl terminal purity of the diol monomermixture obtained by the decomposition of the polycarbonate diol with analkali). Ethanol and potassium hydroxide are added to a polycarbonatediol and heated for 1 hour in a water bath at 100° C., thereby obtaininga reaction mixture. The obtained reaction mixture is cooled to roomtemperature and then neutralized using hydrochloric acid. The resultantneutralized solution is analyzed by gas chromatography (GC). It ispossible that calculation of a precise weight percentage is difficult,because in some cases not all peaks ascribed to the polycarbonate diolcan be identified by the GC analysis. Therefore, in the presentinvention, “a primary hydroxyl terminal purity of 99.0% by weight ormore” means that a value calculated by the following formula, which usesdata obtained by the GC analysis, is 99.0 or more: (sum of the areas ofpeaks ascribed to the diol monomers having primary hydroxyl groups atboth terminals thereof)÷(sum of all peak areas exclusive of the areas ofthe peaks ascribed to the solvent used for diluting a sample andascribed to the internal standard which is optionally added to thesample)×100.

Hereinbelow, a method for producing the polycarbonate diol of thepresent invention is explained. As explained below in detail, thepolycarbonate diol can be produced by effecting a transesterificationreaction between an organic carbonate compound and at least one diolmonomer selected from the group consisting of 1,5-pentanediol and1,6-hexanediol in the presence or absence of a transesterificationcatalyst. If desired, additional diol monomer(s) may also be used inaddition to the above-mentioned at least one diol monomer.

At present, commercially produced 1,5-pentanediol contains1,5-hexanediol and 1,4-cyclohexanediol, each in an amount of 0.2 to 1%by weight. These impurities (i.e., 1,5-hexanediol and1,4-cyclohexanediol) contained in 1,5-pentanediol have secondaryhydroxyl groups and hence exhibit only low reactivity during atransesterification reaction for producing a polycarbonate diol.Therefore, when a polycarbonate diol is produced using 1,5-pentanediolas a raw material, the impurities (exhibiting low reactivity) are likelyto form the terminal groups of the polycarbonate diol. As a result, theproduced polycarbonate diol contains polycarbonate diol chains havingsecondary hydroxyl groups at the terminals thereof. Such a polycarbonatediol causes a lowering of the polymerization reaction rate of apolyurethane-forming reaction. Also, such a polycarbonate diol adverselyaffects the rate of a polymerization reaction for producing a polyesterelastomer.

The purity of 1,5-pentanediol is preferably not less than 99.0% byweight, more preferably not less than 99.5% by weight. The purity of1,5-pentanediol can be determined by gas chromatography (GC).

As mentioned above, 1,5-pentanediol is likely to contain impurity diolshaving a secondary hydroxyl groups. The total amount of diol monomershaving secondary hydroxyl groups is preferably less than 0.5% by weight,more preferably less than 0.3% by weight, based on the weight of1,5-pentanediol. 1,5-Pentanediol may contain other diol monomers havingprimary hydroxyl groups at both terminals thereof (for example,1,3-propanediol, 1,4-butanediol, 1,9-nonanediol,3-methyl-1,5-pentanediol, 1,4-cyclohexanedimethanol). Further,1,5-pentanediol may contain compounds which cause no adverse effects onthe synthesis of the polycarbonate diol, for example, cyclic ethersgenerated by the dehydration of 1,5-pentanediol. In addition, lactones,such as δ-valerolactone; hydroxycarboxylic acids, such as5-hydroxyvaleric acid; and monoalcohols, such as pentanol, are likely tobe by-produced during the production of 1,5-pentanediol. These compoundsmay be contained in 1,5-pentanediol, and the total content of thesecompounds in 1,5-pentanediol is preferably not more than 0.5% by weight,more preferably not more than 0.3% by weight.

1,5-Pentanediol which is suitable for producing the polycarbonate diolof the present invention can be obtained by direct hydrogenation ofglutaric acid, using a ruthenium/tin catalyst (i.e., by hydrogenatingglutaric acid and/or an ester of glutaric acid with a lower alcohol(having 1 to 6 carbons) in the presence of a ruthenium/tin catalyst); orby hydrogenation of a glutaric acid ester, using a copper/chromiumcatalyst.

With respect to the form of glutaric acid which can be easily obtainedby a commercial process, there can be mentioned a mixture of glutaricacid, succinic acid and adipic acid, wherein the mixture is by-producedduring the production of adipic acid by subjecting cyclohexanone and/orcyclohexanol to oxidation with nitric acid. This mixture is subjected toeither a direct hydrogenation or an esterification followed by ahydrogenation, to thereby obtain a diol monomer mixture, and the diolmonomer mixture is then subjected to purification, for example, bydistillation, to thereby obtain 1,5-pentanediol which is suitable forproducing the polycarbonate diol.

On the other hand, at present, commercially produced 1,6-hexanediolcontains impurities having secondary hydroxyl groups, such as1,4-cyclohexanediol, wherein the impurities are contained in an amountof from 0.5 to 2% by weight. The impurities contained in 1,6-hexanediol(such as 1,4-cyclohexanediol, which has secondary hydroxyl groups)exhibit only low reactivity during a transesterification reaction forproducing a polycarbonate diol. Therefore, when a polycarbonate diol isproduced using 1,6-hexanediol as a raw material, the impurities(exhibiting low reactivity) are likely to form the terminal groups ofthe polycarbonate diol. As a result, the produced polycarbonate diolcontains polycarbonate diol chains having secondary hydroxyl groups atthe terminals thereof. Such a polycarbonate diol causes a lowering ofthe polymerization reaction rate of a polyurethane-forming reaction,making it impossible to obtain a polyurethane having a satisfactorymolecular weight. Also, such a polycarbonate diol adversely affects therate of a polymerization reaction for producing a polyester elastomer.

The purity of 1,6-hexanediol is preferably not less than 99.0% byweight, more preferably not less than 99.4% by weight, still morepreferably not less than 99.8% by weight. The purity of 1,6-hexanediolcan be determined by gas chromatography (GC).

The amount of 1,4-cyclohexanediol in 1,6-hexanediol is preferably 0.5%by weight or less, more preferably 0.1% by weight or less, based on theweight of 1,6-hexanediol. 1,6-Hexanediol may contain other diol monomershaving primary hydroxyl groups at both terminals thereof (for example,1,3-propanediol, 1,4-butanediol, 1,9-nonanediol,3-methyl-1,5-pentanediol, 1,4-cyclohexanedimethanol). Further,1,6-hexanediol may contain compounds which cause no adverse effects onthe synthesis of the polycarbonate diol, for example, cyclic ethersgenerated by the dehydration of 1,6-hexanediol. In addition, lactones,such as δ-valerolactone and ε-caprolactone; hydroxycarboxylic acids,such as 5-hydroxyvaleric acid and 6-hydoxycaproic acid; andmonoalcohols, such as pentanol and hexanol, are likely to be by-producedduring the production of 1,6-hexanediol. These compounds may becontained in 1,6-hexanediol, and the total content of these compounds in1,6-hexanediol is preferably not more than 0.5% by weight, morepreferably not more than 0.3% by weight.

1,6-Hexanediol which is suitable for producing the polycarbonate diol ofthe present invention can be obtained by direct hydrogenation of adipicacid, using a ruthenium/tin catalyst (i.e., by hydrogenating adipic acidand/or an ester of adipic acid with a lower alcohol (having 1 to 6carbons) in the presence of a ruthenium/tin catalyst); or byhydrogenation of an adipic acid ester, using a copper/chromium catalyst.

As adipic acid which can be easily obtained by a commercial process,there can be mentioned adipic acid which is obtained by subjectingcyclohexanone and/or cyclohexanol to oxidation with nitric acid in thepresence of a catalyst comprising copper and vanadium to thereby formadipic acid, followed by the crystal deposition thereof. The purity ofadipic acid is preferably 99.0% by weight or more, more preferably 99.4%by weight or more, and most preferably 99.8% by weight or more. Inaddition, there can also be used a mixture of glutaric acid, succinicacid and adipic acid, wherein the mixture is by-produced during theproduction of adipic acid. This mixture is subjected to either a directhydrogenation or an esterification, followed by hydrogenation, tothereby obtain a diol monomer mixture, and the diol monomer mixture isthen subjected to purification, for example, by distillation, to therebyobtain 1,6-hexanediol which is suitable for producing the polycarbonatediol.

Conventionally, 1,6-hexanediol is produced from an organic acid mixturecontaining adipic acid, hydroxycapronic acid and glutaric acid, whereinthe organic acid mixture is by-produced during the production ofcyclohexanone and/or cyclohexanol by oxidation of cyclohexane with air.For producing 1,6-hexanediol, the organic acid mixture is subjected toesterification and then to hydrogenation in the presence of a coppercatalyst to thereby obtain 1,6-hexanediol, and the obtained1,6-hexanediol is purified by distillation. 1,6-Hexanediol which isconventionally produced in the above-mentioned manner contains1,4-cyclohexanediol, and such 1,6-hexanediol is not suitable as a rawmaterial for producing the polycarbonate diol of the present invention.The boiling point of 1,4-cyclohexanediol and the boiling point of1,6-hexanediol are very close to each other and, therefore, it isdifficult to decrease the amount of 1,4-cyclohexanediol in1,6-hexanediol to the above-mentioned preferred level (i.e., 0.5% byweight or less) by distillation.

By contrast, when 1,6-hexanediol is obtained by a method in which adipicacid is obtained by the oxidation of cyclohexanone and/or cyclohexanolwith nitric acid, and the adipic acid is subjected to either a directhydrogenation or an esterification followed by hydrogenation to therebyobtain 1,6-hexanediol, the obtained 1,6-hexanediol has only a very smallcontent of impurities (such as the above-mentioned diol monomers havingsecondary OH groups) and hence is suitable as a raw material forproducing the polycarbonate diol of the present invention.

Further, if desired, a diol monomer mixture containing a plurality ofdifferent types of diol monomers each having primary OH groups at bothterminals thereof can be used as a raw material for producing thepolycarbonate diol of the present invention. In such case, it ispreferred that the so-called primary hydroxyl terminal purity of thediol monomer mixture (which has the same meaning as defined with respectto the mixture of diol monomers obtained by the decomposition of thepolycarbonate diol) is 99.0% by weight or more, more preferably 99.5% byweight or more, still more preferably 99.8% by weight or more.

In addition to the at least one diol monomer selected from the groupconsisting of 1,5-pentanediol and 1,6-hexanediol, if desired, other diolmonomers may also be used as a raw material for producing thepolycarbonate diol of the present invention. Specific examples of suchother diol monomers include 1,3-propanediol, 1,4-butanediol,1,9-nonanediol, 3-methyl-1,5-pentanediol and 1,4-cyclohexanedimethanol.With respect to the molar ratio of 1,5-pentanediol or 1,6-hexanediol toother diol monomers, there is no particular limitation as long as thetotal amount of 1,5-pentanediol and 1,6-hexanediol is 50% by mole ormore, based on the total molar amount of all diol monomers.

In the present invention, the R groups in 50 to 100% by mole of therecurring units represented by formula (1) above must be comprised ofdivalent groups derived from at least one diol monomer selected from thegroup consisting of 1,5-pentanediol and 1,6-hexanediol. Other examplesof R groups in the recurring units of formula (1) include divalentgroups derived from 1,3-propanediol, 1,4-butanediol, 1,9-nonanediol,3-methyl-1,5-pentanediol and 1,4-cyclohexanedimethanol.

An especially preferred polycarbonate diol is a copolycarbonate diolsynthesized from a mixture of 1,6-hexanediol and at least one diolmonomer selected from the group consisting of 1,4-butanediol and1,5-pentanediol. Such a copolycarbonate diol is preferred because athermoplastic polyurethane which is prepared using such acopolycarbonate diol exhibits excellent low temperature properties andexcellent impact resilience.

If desired, the polycarbonate diol of the present invention may be amultifunctional polycarbonate diol which is synthesized using a mixtureof the above-mentioned at least one essential diol monomer(1,5-pentanediol and/or 1,6-hexanediol) and a small amount of a compoundhaving 3 or more hydroxyl groups per molecule, such astrimethylolethane, trimethylolpropane or pentaerythritol, each of whichis a polyol having primary hydroxyl groups. When polyols are used in alarge amount, the polyols are likely to form cross-linkages and causegelation. Therefore, it is preferred that the amount of the polyol isnot more than 10% by mole, based on the total molar amount of the diolmonomers.

The number average molecular weight (Mn) of the polycarbonate diol ofthe present invention may vary depending on the use of the polycarbonatediol, but it is generally in the range of from 300 to 50,000, preferablyfrom 600 to 20,000. In the present invention, the number averagemolecular weight of the polycarbonate diol is determined by thefollowing method. The OH value of the polycarbonate diol is determinedby the conventional neutralization titration method (JIS K 0070-1992),which uses acetic acid anhydrate, pyridine and an ethanol solution ofpotassium hydroxide. The number average molecular weight (Mn) iscalculated from the OH value in accordance with the following formula:Mn=56.1×2×1,000÷OH value

As explained above, the polycarbonate diol of the present invention canbe produced by effecting a transesterification reaction between anorganic carbonate compound and at least one diol monomer selected fromthe group consisting of 1,5-pentanediol and 1,6-hexanediol in thepresence or absence of a transesterification catalyst. If desired,additional diol monomer(s) may also be used in addition to theabove-mentioned at least one diol monomer. Examples of organic carbonatecompounds include ethylene carbonate, dimethyl carbonate, diethylcarbonate and diphenyl carbonate.

A method for producing a polycarbonate diol without the use of acatalyst is exemplified below, wherein the method uses ethylenecarbonate as the organic carbonate compound.

The polycarbonate diol is produced by a method comprising the followingtwo steps. First, a diol monomer and ethylene carbonate are mixedtogether so that the molar ratio of diol monomer to ethylene carbonateis in the range of from 20:1 to 1:10. The resultant mixture is heated at100 to 300° C. under atmospheric or reduced pressure to effect areaction while distilling off the by-produced ethylene glycol andunreacted ethylene carbonate, thereby obtaining a low molecular weightpolycarbonate diol having 2 to 10 diol monomer units. Subsequently, theobtained low molecular weight polycarbonate diol is subjected toself-condensation reaction at 100 to 300° C. under reduced pressurewhile distilling off the unreacted diol monomer and ethylene carbonate.The by-produced diols which are the same as the raw material diolmonomers are also distilled off during the self-condensation reaction,thereby obtaining a polycarbonate diol having a desired molecularweight.

Next, a method for producing a polycarbonate diol by using atransesterification catalyst is exemplified below.

Among the conventional, transesterification catalysts, an alkali metalalcoholate is preferred because it can be obtained at a low cost and canbe easily removed from the reaction products. An alkali metal alcoholatecan be removed, for example, by a reaction thereof with carbon dioxideor by simple washing. Alternatively, an alkali metal alcoholate can beremoved either by a treatment with an organic or inorganic acid or by acontact with a sulfonated acidic resin. Examples of other catalystswhich can be used for producing the polycarbonate diol of the presentinvention include transition metal alcoholates (which may be doublesalts thereof), such as Ti(OR)₄, MgTi(OR)₆, Pb(OR)₂ (wherein R is anorganic group), and metal oxides, such as CaO, ZnO and SnOR₂ (R is sameas defined above), and a combination of these compounds. When, forexample, diphenyl carbonate is used as an organic carbonate, aneffective amount of the catalyst is from 0.001 to 0.5% by weight,preferably 0.01% by weight, based on the weight of the reaction bulk.

The polymerization reaction is preferably performed in two steps as inthe case of the reaction performed without using a catalyst.Specifically, in step 1, a diol monomer and ethylene carbonate are mixedtogether so that the molar ratio of diol monomer to ethylene carbonateis in the range of from 20:1 to 1:10. The resultant mixture is heated at100 to 200° C. under atmospheric or reduced pressure to effect areaction while distilling off the by-produced alcohols derived from theorganic carbonate, thereby obtaining a low molecular weightpolycarbonate diol. Subsequently, in step 2, the obtained low molecularweight polycarbonate diol is heated at 150 to 300° C. under reducedpressure to effect a self-condensation reaction. The reaction isterminated when the molecular weight of the reaction product has reacheda desired value (which can be easily checked by measuring the viscosityof the reaction mixture).

When the polycarbonate diol of the present invention is used forproducing a thermoplastic polyurethane or a polyester elastomer, thedesired polymerization reactions can proceed at high rate, and thereforethe polycarbonate diol can be advantageously used as a raw material forproducing a thermoplastic polyurethane and a polyester elastomer,especially for producing a thermoplastic polyurethane.

Accordingly, the thermoplastic polyurethane of the present invention canbe obtained by copolymerizing the polycarbonate diol of the presentinvention and a polyisocyanate.

Examples of polyisocyanates used for producing the thermoplasticpolyurethane of the present invention include conventional aromaticdiisocyanates, such as 2,4-tolylene diisocyanate, 2,6-tolylenediisocyanate, a mixture of 2,4-tolylene diisocyanate and 2,6-tolylenediisocyanate (TDI), diphenylmethane-4,4′-diisocyanate (MDI),naphthalene-1,5-diisocyanate (NDI), 3,3′-dimethyl-4,4′-biphenylenediisocyanate, crude TDI, poly-methylenepolyphenyl isocyanate, crude MDI,xylylene diisocyanate (XDI) and phenylene diisocyanate; conventionalaliphatic diisocyanates, such as 4,4′-methylene-biscyclohexyldiisocyanate (hydrogenated MDI), hexamethylene diisocyanate (HMDI),isophorone diisocyanate (IPDI) and cyclohexane diisocyanate(hydrogenated XDI); and modified products thereof, such as isocyanurateproducts, carbodimide products and biuret products.

In the present invention, if desired, a chain extender may be used as acopolymerizable component. As the chain extender, there may be employeda customary chain extender used for producing a polyurethane, asdescribed in, for example, “Saishin Poriuretan Oyo-Gijutsu (LatestApplication Techniques of Polyurethane)” edited by Keiji Iwata, pp.25–27, CMC, Japan, 1985. Examples of chain extenders include water, alow molecular weight polyol, a polyamine and the like. Depending on theuse of the thermoplastic polyurethane, if desired, a conventional highmolecular weight polyol may also be used in combination with thepolycarbonate diol of the present invention as long as the properties ofthe produced polyurethane are not adversely affected. As theconventional high molecular weight polyol, there may be employed thosewhich are described in, for example, pp. 12–23 of “Poriuretan Foumu(Polyurethane Foam)” by Yoshio Imai, published by Kobunshi Kankokai,Japan, 1987. Examples of high molecular weight polyols include apolyester polyol and a polyether carbonate having a polyoxyalkylenechain (i.e., a polyether carbonate polyol).

Specifically, a low molecular weight polyol used as a chain extender isgenerally a diol monomer having a molecular weight of not more than 300.Examples of such low molecular weight polyols include aliphatic diols,such as ethylene glycol, 1,3-propanediol, 1,4-butanediol,1,5-pentanediol, 1,6-hexanediol, neopentyl glycol and 1,10-decanediol.

Further examples of low molecular weight polyols used as a chainextender include alicyclic diols, such as 1,1-cyclohexanedimethanol,1,4-cyclohexanedimethanol and tricyclodecanedimethanol; xylylene glycol,bis(p-hydroxy)diphenyl, bis(p-hydroxyphenyl)propane,2,2-bis[4-(2-hydroxyethoxy)phenyl]propane,bis[4(2-hydroxy)phenyl]sulfone and1,1-bis[4-(2-hydroxyethoxy)phenyl]cyclohexane. As a chain extender,ethylene glycol and 1,4-butanediol are preferred.

For producing the thermoplastic polyurethane of the present invention, aurethane-forming technique known in the art may be employed. Forexample, the polycarbonate diol of the present invention is reacted withan organic polyisocyanate at a temperature of from room temperature to200° C. to form a thermoplastic polyurethane. When a chain extender isoptionally used, a chain extender may be added to the reaction systemeither before initiating the reaction or during the reaction. For aspecific method for producing a thermoplastic polyurethane, referencecan be made to U.S. Pat. No. 5,070,173.

In the polyurethane-forming reaction, a conventional polymerizationcatalyst, such as a tertiary amine and an organic salt of a metal, e.g.,tin or titanium, may be employed (see, for example, “Poriuretan Jushi(Polyurethane Resin)” written by Keiji Iwata, pages 23 to 32, publishedin 1969 by The Nikkan Kogyo Shimbun, Ltd., Japan). Thepolyurethane-forming reaction may be performed in a solvent. Preferredexamples of solvents include dimethylformamide, diethylformamide,dimethylacetamide, dimethylsulfoxide, tetrahydrofuran, methyl isobutylketone, dioxane, cyclohexanone, benzene, toluene and ethyl cellosolve.

In the polyurethane-forming reaction, a compound having only one activehydrogen atom which is capable of reacting with an isocyanate group, forexample, a monohydric alcohol, such as ethyl alcohol or propyl alcohol,and a secondary amine, such as diethylamine or di-n-propylamine, may beused as a reaction terminator.

In the present invention, it is preferred that stabilizers, such as heatstabilizers (for example, antioxidant) and light stabilizers, are addedto the thermoplastic polyurethane.

Examples of antioxidants (heat stabilizers) include aliphatic, aromaticor alkyl-substituted aromatic esters of phosphoric acid or phosphorousacid; hypo-phosphinic acid derivatives; phosphorus-containing compounds,such as phenylphosphonic acid, phenylphosphinic acid, diphenylphosphonicacid, polyphosphonate, dialkylpentaerythritol diphosphite and adialkylbisphenol A diphosphite; phenol derivatives, especially, hinderedphenol compounds; sulfur-containing compounds, such as thioether typecompounds, dithioacid salt type compounds, mercaptobenzimidazole typecompounds, thiocarbanilide type compounds and thiodipropionic acidesters; and tin-containing compounds, such as tin malate and dibutyltinmonooxide.

In general, antioxidants can be classified into primary, secondary andtertiary antioxidants. As hindered phenol compounds used as a primaryantioxidant, Irganox 1010 (trade name) (manufactured and sold byCIBA-GEIGY, Switzerland) and Irganox 1520 (trade name) (manufactured andsold by CIBA-GEIGY, Switzerland) are preferred. As phosphorus-containingcompounds used as a secondary antioxidant, PEP-36, PEP-24G and HP-10(each being a trade name) (each manufactured and sold by ASAHI DENKAK.K., Japan) and Irgafos 168 (trade name) (manufactured and sold byCIBA-GEIGY, Switzerland) are preferred. Further, as sulfur-containingcompounds used as a tertiary antioxidant, thioether compounds, such asdilaurylthiopropionate (DLTP) and distearylthiopropionate (DSTP) arepreferred.

Examples of light stabilizers include UV absorber type light stabilizersand radical scavenger type light stabilizers. Specific examples of UVabsorber type light stabilizers include benzotriazole compounds andbenzophenone compounds. Specific examples of radical scavenger typelight stabilizers include hindered amine compounds.

The above-exemplified stabilizers can be used individually or incombination. The stabilizers are added to the thermoplastic polyurethanein an amount of from 0.01 to 5 parts by weight, preferably from 0.1 to 3parts by weight, more preferably from 0.2 to 2 parts by weight, relativeto 100 parts by weight of the thermoplastic polyurethane.

If desired, a plasticizer may be added to the thermoplastic polyurethaneof the present invention. Examples of plasticizers include phthalicesters, such as dioctyl phthalate, dibutyl phthalate, diethyl phthalate,butylbenzyl phthalate, di-2-ethylhexyl phthalate, diisodecyl phthalate,diundecyl phthalate and diisononyl phthalate; phosphoric esters, such astricresyl phosphate, triethyl phosphate, tributyl phosphate,tri-2-ethylhexyl phosphate, trimethylhexyl phosphate, tris-chloroethylphosphate and tris-dichloropropyl phosphate; aliphatic esters, such asoctyl trimellitate, isodecyl trimellitate, trimellitic esters,dipentaerythritol esters, dioctyl adipate, dimethyl adipate,di-2-ethylhexyl azelate, dioctyl azelate, dioctyl sebacate,di-2-ethylhexyl sebacate and methylacetyl ricinoleate; pyromelliticesters, such as octyl pyromellitate; epoxy plasticizers, such asepoxidized soyabean oil, epoxidized linseed oil and epoxidized fattyacid alkyl ester; polyether plasticizers, such as adipic ether ester andpolyether; liquid rubbers, such as liquid NBR, liquid acrylic rubber andliquid polybutadiene; and non-aromatic paraffin oil.

The above-exemplified plasticizers may be used individually or incombination. The amount of the plasticizer added to the thermoplasticpolyurethane is appropriately chosen in accordance with the requiredhardness and properties of the thermoplastic polyurethane; however, ingeneral, it is preferred that the plasticizer is used in an amount offrom 0.1 to 50 parts by weight, relative to 100 parts by weight of thethermoplastic polyurethane.

In addition, other additives, such as inorganic fillers, lubricants,colorants, silicon oil, foaming agents, flame retardants and the like,may be added to the thermoplastic polyurethane of the present invention.Examples of inorganic fillers include calcium carbonate, talc, magnesiumhydroxide, mica, barium sulfate, silicic acid (white carbon), titaniumoxide and carbon black. These additives may be added to thethermoplastic polyurethane of the present invention in an amount whichis generally used for the conventional thermoplastic polyurethane.

The Shore D hardness of the thermoplastic polyurethane of the presentinvention is preferably in the range of from 20 to 70, more preferablyfrom 25 to 50. When the Shore D hardness is less than 20, heat stabilityand scratch resistance become low. On the other hand, when the Shore Dhardness is more than 70, low temperature properties and softness becomeunsatisfactory.

Further, the melt flow rate (as measured at 230° C. under a load of 2.16kg; hereinafter, abbreviated to “MFR”) of the thermoplastic polyurethaneof the present invention is preferably from 0.5 to 100 g/10 minutes,more preferably from 5 to 50 g/10 minutes, still more preferably from 10to 30 g/10 minutes. When MFR is less than 0.5 g/10 minutes, theinjection moldability of the polyurethane becomes poor and the injectionmolding is likely to result in “short shot” (that is, the filling of themold cavity becomes incomplete). On the other hand, when MFR is morethan 100 g/10 minutes, not only the mechanical properties (such astensile strength and elongation at break) and abrasion resistance, butalso low temperature properties are lowered.

With respect to the molecular weight of the thermoplastic polyurethane,it is preferred that each of the number average molecular weight (Mn)and the weight average molecular weight (Mw) of the thermoplasticpolyurethane is in the range of from 10,000 to 200,000. Each of Mn andMw is measured by GPC analysis, using a calibration curve obtained withrespect to standard polystyrene samples.

Hereinbelow, a method for producing a polyester elastomer by using thepolycarbonate diol of the present invention is explained. A polyesterelastomer can be produced in accordance with the various known methods.For example, the polycarbonate diol of the present invention, adicarboxylic ester or a combination of a dicarboxylic acid and a chainextender, and an antioxidant are charged into a reactor together with acatalyst (for example, at least one catalyst selected from the groupconsisting of tetrabutyl titanate, magnesium acetate and calciumacetate), and a reaction is effected at 100 to 250° C. under atmosphericpressure to 0.01 kPa, thereby obtaining a polyester elastomer. Withrespect to the chain extender and the antioxidant, those which areexemplified above in connection with the thermoplastic polyurethane canbe used. The antioxidant has the effect of preventing the discolorationof the polyester elastomer during the production thereof, and it ispreferred that the antioxidant is added to the polyester elastomerduring the production thereof. The use of a catalyst can decrease therequired polymerization time, thereby suppressing the heat deteriorationof the polyester elastomer during the production thereof. If desired, alight stabilizer may be added to the produced polyester elastomer. Withrespect to the light stabilizer, those which are exemplified above inconnection with the thermoplastic polyurethane can be used. As anexample of a dicarboxylic ester used for producing the polyesterelastomer, there can be mentioned dimethyl terephthalate. Representativeexamples of dicarboxylic acids used for producing the polyesterelastomer include 2,6-naphthalene dicarboxylic acid and terephthalicacid.

With respect to the molecular weight of the polyester elastomer, it ispreferred that each of the number average molecular weight (Mn) and theweight average molecular weight (Mw) of the polyester elastomer is inthe range of from 10,000 to 200,000. Each of Mw and Mn is measured byGPC analysis, using a calibration curve obtained with respect tostandard polystyrene samples.

An example of a method for producing a polyester elastomer by reactingthe polycarbonate diol of the present invention with a dicarboxylicester or dicarboxylic acid is as follows. The polycarbonate diol of thepresent invention is mixed with a dicarboxylic ester or dicarboxylicacid, and optionally added thereto is at least one member selected fromthe group consisting of a chain extender, an antioxidant, a lightstabilizer and a catalyst, and a polymerization reaction is effected byheating the resultant mixture at a predetermined temperature in anitrogen gas atmosphere under atmospheric pressure while distilling offthe by-produced alcohol or water. The pressure of the reaction system ischanged to reduced pressure in accordance with an increase in the degreeof polymerization of the reaction product, and if desired, thetemperature is elevated to distill off the by-produced alcohol or waterand a part of the chain extender. When the degree of polymerization ofthe reaction product has reached a desired value, the pressure of thereaction system is increased to atmospheric pressure in a nitrogen gasatmosphere, and the heating is terminated, followed by cooling of thereaction system to room temperature, thereby terminating the reaction.With respect to the specific methods for producing a polyesterelastomer, reference can be made to, for example, French Patent No.2,253,044 and Unexamined Japanese Patent Application Laid-OpenSpecification Nos. Sho 50-40657 and Sho 50-45895.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinbelow, the present invention will be described in more detail withreference to the following Reference Example, Examples and ComparativeExamples; however, they should not be construed as limiting the scope ofthe present invention.

In the following Reference Example, Examples and Comparative Examples,various measurements and analyses were conducted by the followingmethods.

The primary terminal OH ratio of a polycarbonate diol was measured bythe following method. 70 g to 100 g of a polycarbonate diol was weighedout and placed in a 300 cc eggplant shaped flask. Using a rotaryevaporator connected to a trap bulb for recovering a fraction, thepolycarbonate diol in the eggplant shaped flask was heated in a heatingbath at about 180° C. under a pressure of 0.1 kPa or less while stirringto thereby obtain, in the trap bulb, a fraction in an amount which isapproximately 1 to 2% by weight of the polycarbonate diol. That is,approximately 1 g (0.7 g to 2 g) of a fraction was obtained, and theobtained fraction was recovered using approximately 100 g (95 g to 105g) of ethanol as a solvent, thereby obtaining a sample solution. Theobtained sample solution was analyzed by gas chromatography (GC) tothereby obtain a chromatogram, and the primary terminal OH ratio wascalculated from the peak areas in accordance with the following formula:Primary terminal OH ratio (%)=(sum of the areas of the peaks ascribed todiol monomers having primary hydroxyl groups at both terminalsthereof)÷(sum of the areas of the peaks ascribed to the alcoholsinclusive of diol monomers (but exclusive of ethanol))×100.

The analysis by GC was conducted under the following conditions.

Conditions for GC

-   Column: DB-WAX (column length: 30 m, film thickness: 0.25 μm)    (manufactured and sold by J & W Scientific, U.S.A.)-   Heating conditions: the temperature was elevated from 60° C. to 250°    C.-   Detector: FID (flame ionization detector)

The primary hydroxyl terminal purity of a polycarbonate diol wasdetermined by the following method using an alkali decomposition.Approximately 1.0 g of a polycarbonate diol was weighed out and placedin a 100 cc eggplant shaped flask. 30 g of ethanol and 3.95 g ofpotassium hydroxide were added to the polycarbonate diol and heated for1 hour in a heating bath at about 100° C. while stirring, therebyobtaining a reaction mixture. The obtained reaction mixture was cooledto room temperature and then neutralized using hydrochloric acid. Theresultant neutralized mixture was chilled in a refrigerator for 1 hourto thereby precipitate potassium chloride formed by neutralization. Theprecipitated potassium chloride was removed by filtration and theresultant filtrate was analyzed by GC under the same conditions asmentioned above to thereby determine the weight percentage of the diolmonomers having primary hydroxyl groups at both terminals thereof, basedon the weight of the mixture of diol monomers in the filtrate.

The number average molecular weight (Mn) of the polycarbonate diol wasdetermined by the following method. The OH value of the polycarbonatediol was determined by the conventional neutralization titration method(JIS K 0070-1992), which uses acetic acid anhydrate, pyridine and anethanol solution of potassium hydroxide. The number average molecularweight (Mn) was calculated from the OH value in accordance with thefollowing formula:Mn=56.1×2×1,000÷OH value.

The number average molecular weight and weight average molecular weightof a thermoplastic polyurethane were determined by GPC (gel permeationchromatography), using a calibration curve obtained with respect tostandard polystyrene samples.

In the Examples and the Comparative Examples, various properties of athermoplastic polyurethane were measured by the following methods.

(1) Shore ‘D’ Hardness [−]:

Shore ‘D’ hardness was measured in accordance with ASTM D2240, D type,at 23° C.

(2) Melt Flow Rate (MFR) [g/10 min]:

Melt flow rate was measured in accordance with ASTM D1238, under a loadof 2.16 kg at 230° C.

(3) Tensile Strength [kgf/cm²]:

Tensile strength was measured in accordance with JIS K6251 (using adumbbell No. 3 prescribed therein). A pressed sheet having a thicknessof 2 mm was used as a test sample.

(4) Elongation [%]:

Elongation was measured in accordance with JIS K6251 (using a dumbbellNo. 3 prescribed therein). A pressed sheet having a thickness of 2 mmwas used as a test sample.

(5) Impact Resilience [%]:

Impact resilience was measured in accordance with JIS K6255 (using aLübke pendulum, 23° C.).

(6) Brittleness Temperature [° C.]:

Brittleness temperature was measured in accordance with JIS K6261.Specifically, the “t100 temperature” determined by the following methodusing the Gehman torsion test was used as the brittleness temperature.By using a Gehman torsion tester, the torsional modulus of a testspecimen (width: 3 mm, length: 38 mm, thickness: 2 mm) was measured at23±3° C. and at various temperatures which are lower than 23° C., andthe ratio of the torsional modulus at each low temperature to thetorsional modulus at 23±3° C. (the ratio is hereinafter referred to asthe “relative modulus”) was calculated in accordance with the followingformula:${RM} = {\frac{\left( {180 - \theta_{1}} \right)}{\theta_{1}}/\frac{\left( {180 - \theta_{0}} \right)}{\theta_{0}}}$

wherein,

-   -   RM: relative modulus,    -   θ₀: torsion angle of the test specimen at 23±3 C, and    -   θ₁: torsion angle of the test specimen at the low temperature.

The temperature (low temperature) at which RM (relative modulus)calculated by the formula above became 100 was defined as the “t100temperature”, and this temperature was used as the brittlenesstemperature.

REFERENCE EXAMPLE 1 Synthesis of 1,4-butanediol, 1,5-pentanediol and1,6-haxanediol

An aqueous solution of a by-produced dicarboxylic acid mixture wasobtained from a commercial plant for producing adipic acid, and washeated at about 120° C. for 1 hour and, then, at a temperature of from170 to 175° C. for 30 minutes while stirring, thereby obtaining adicarboxylic acid mixture in solid form. The obtained dicarboxylic acidmixture was dissolved in ion-exchanged water to thereby obtain anaqueous dicarboxylic acid mixture solution having a dicarboxylic acidmixture content of 38% by weight. 1,000 g of the dicarboxylic acidmixture solution was contacted with 300 g of a styrene polymer typecation exchange resin (trade name: Amberlite IR-120B) (manufactured andsold by ORGANO CORP., Japan) for 2 hours, followed by removing of thecation exchange resin by filtration. The resultant filtrate (an aqueousdicarboxylic acid mixture solution) was obtained for subsequent use as araw material for the hydrogenation reaction. The dicarboxylic acidconcentration of the filtrate was 38% by weight, and the dicarboxylicacid comprised 20% by weight of succinic acid, 50% by weight of glutaricacid and 30% by weight of adipic acid.

An activated carbon (carrier) was impregnated with chloroplatinic acidhexahydrate, tin(II) chloride and ruthenium trichloride trihydrate,followed by drying of the resultant impregnated activated carbon. Then,the impregnated activated carbon was subjected to reduction treatment ina hydrogen atmosphere to thereby obtain a hydrogenation catalyst. Theobtained hydrogenation catalyst comprised an activated carbon havingcarried thereon 6.0% by weight of ruthenium, 5.0% by weight of tin and3.5% by weight of platinum. By using the hydrogenation catalyst, thehydrogenation of the above-mentioned dicarboxylic acid mixture wasperformed in the following manner.

600 g of the above-mentioned aqueous dicarboxylic acid mixture solutionand 10 g of the above-mentioned catalyst were charged into a 1,000 mlautoclave made of SUS 316. The atmosphere in the autoclave was purgedwith nitrogen at room temperature and, then, pressurized hydrogen gaswas introduced into the autoclave to increase the internal pressurethereof to 2 MPa, and the internal temperature of the autoclave waselevated to 180° C. After the internal temperature of the autoclavereached 180° C., pressurized hydrogen gas was further introduced intothe autoclave to increase the internal pressure thereof to 15 MPa, andthen a hydrogenation reaction was performed under the above-mentionedinternal pressure for 30 hours. After completion of the hydrogenationreaction, a hydrogenation reaction mixture containing the catalyst wassubjected to filtration, to thereby recover the catalyst. The recoveredcatalyst and 600 g of the above-mentioned aqueous dicarboxylic acidmixture solution were charged into the autoclave, and a hydrogenationreaction was performed under substantially the same conditions asmentioned above. In this way, the procedure for the hydrogenation of thedicarboxylic acid mixture was repeated 9 times in total (i.e., 10 runsof the hydrogenation were performed), thereby obtaining approximately 6kg of a hydrogenation reaction mixture.

The obtained hydrogenation reaction mixture was heated to 109° C. underatmospheric pressure to distill off a large portion of water containedin the mixture. The residual mixture was subjected to distillation usinga multi-stage distillation column having 12 stages. By the distillation,water and low boiling point compounds, such as pentanol, were distilledoff, thereby obtaining a purified diol monomer mixture. The purifieddiol monomer mixture obtained was further subjected to distillationunder reduced pressure using a multi-stage distillation column having 35stages. By the distillation, 1,4-butanediol containing a very smallamount of 1,5-pentanediol was recovered as a distillation fraction.

The amount of the recovered 1,4-butanediol was 342 g. The recovered1,4-butanediol was analyzed by gas chromatography and it was found thatthe recovered 1,4-butanediol had a purity of 99.1% by weight andcontained 0.48% by weight of 1,5-pentanediol as an impurity.

A residual liquid obtained in the column bottom after the distillationrecovery of 1,4-butanediol was subjected to distillation under reducedpressure using a multi-stage distillation column having 35 stages. Bythe distillation, 1,5-pentanediol containing very small amounts of1,4-butanediol and 1,6-hexanediol was recovered as a distillationfraction.

The amount of the recovered 1,5-pentanediol was 860 g. The recovered1,5-pentanediol was analyzed by gas chromatography and it was found thatthe recovered 1,5-pentanediol had a purity of 99.0% by weight andcontained 0.09% by weight of 1,4-butanediol, 0.29% by weight of1,6-hexanediol, not more than 0.01% by weight of 1,5-hexanediol and notmore than 0.01% by weight of 1,4-cyclohexanediol as impurities. Otherimpurities were compounds having boiling points which are higher thanthat of 1,6-hexanediol, and these other impurities could not beidentified. Accordingly, in the obtained diol monomer, which wascomposed mainly of 1,5-pentanediol, the purity of diol monomers havingprimary hydroxyl groups at both terminals thereof was 99.38% by weight,and the total content of diol monomers having a secondary hydroxyl groupwas not more than 0.02% by weight.

A residual liquid obtained in the column bottom after the distillationrecovery of 1,5-pentanediol was subjected to distillation under reducedpressure using a multi-stage distillation column having 10 stages. Bythe distillation, 1,6-hexanediol containing a very small amount of1,5-pentanediol was recovered as a distillation fraction.

The amount of the recovered 1,6-hexanediol was 476 g. The recovered1,6-hexanediol was analyzed by gas chromatography and it was found thatthe recovered 1,6-hexanediol had a purity of 99.1% by weight andcontained 0.07% by weight of 1,4-butanediol, 0.43% by weight of1,5-pentanediol, not more than 0.01% by weight of 1,5-hexanediol and notmore than 0.01% by weight of 1,4-cyclohexanediol as impurities. Otherimpurities were compounds having boiling points which are higher thanthat of 1,6-hexanediol, and these other impurities could not beidentified.

EXAMPLE 1

236 g (2.0 mol) of 1,6-hexanediol synthesized in Reference Example 1 wascharged in a reaction vessel equipped with a stirrer, a thermometer anda fractionating column. The 1,6-hexanediol in the reaction vessel washeated at 70° C. to 80° C., and 1.84 g (0.08 mol) of metallic sodium wasadded thereto while stirring to effect a reaction. After the metallicsodium was completely reacted, 236 g (2.0 mol) of diethyl carbonate wasintroduced into the reaction vessel, and a reaction was performed underatmospheric pressure while gradually elevating the reaction temperatureup to 160° C. When the reaction temperature was elevated to 95° C. to100° C., ethanol began to be distilled off. The elevation in thereaction temperature from 100° C. up to 160° C. was effected over 6hours. During this period, a mixture of ethanol and about 10% by weight,based on the weight of the mixture, of diethyl carbonate was distilledoff. Then, the pressure within the reaction vessel was lowered to 1.3kPa or less and a reaction was effected at 200° C. for 4 hours whilevigorously stirring and removing distilled ethanol from the reactionvessel. The resultant polymer was cooled, dissolved in dichloromethaneand neutralized with diluted acid. The polymer was then dehydrated withanhydrous sodium sulfate. After removing the solvent from the polymer bydistillation, the polymer was dried at 140° C. under 0.27 to 0.40 kPafor several hours to obtain a polycarbonate diol. The obtainedpolycarbonate diol of 1,6-hexanediol was a white solid product at roomtemperature, and the number average molecular weight thereof was 2,100and the primary terminal OH ratio thereof was 99.6%. Further, theprimary hydroxyl terminal purity thereof, as measured by a method usingan alkali decomposition, was 99.7% by weight. Hereinafter, the obtainedpolymer is referred to as “pc-a”.

EXAMPLES 2 AND 3

Aliphatic copolycarbonate diols (referred to as “pc-b” and “pc-c”) wereindividually produced in substantially the same manner as in Example 1except that 1,4-butanediol (abbreviated to “BDL”), 1,5-petanediol(abbreviated to “PDL”) and 1,6-hexanediol (abbreviated to “HDL”), whichwere synthesized in Reference Example 1, were used in the amountsindicated in Table 1. The properties of the copolycarbonate diols arealso shown in Table 1.

EXAMPLE 4

A polycarbonate diol (of 1,5-pentanediol) was produced in substantiallythe same manner as in Example 1 except that 208 g (2.0 mol) of1,5-petanediol synthesized in Reference Example 1 was used as a diolmonomer. The produced polycarbonate diol of 1,5-pentanediol was a whitesolid product at room temperature, and the number average molecularweight thereof was 2,000 and the primary terminal OH ratio thereof was99.2%. Further, the primary hydroxyl terminal purity thereof, asmeasured by a method using an alkali decomposition, was 99.3% by weight.

COMPARATIVE EXAMPLES 1 TO 3

Aliphatic copolycarbonate diols (referred to as “pc-d”, “pc-e” and“pc-f”) were individually produced in substantially the same manner asin Example 1 except that commercially available diol products, namely a1,4-butanediol product (purity determined by analysis: 98.2%), a1,5-petanediol product (purity determined by analysis: 98.5%) and a1,6-hexanediol product(purity determined by analysis: 98.6%), were usedas diol monomers in the amounts indicated in Table 1. The properties ofthe copolycarbonate diols are also shown in Table 1.

TABLE 1 Amount Amount Amount Primary Primary OH terminal of BDL of PDLof HDL Number average terminal purity as measured by used used usedmolecular weight OH ratio a method using alkali Abbreviation for (g) (g)(g) (Mn) (%) decomposition (wt %) polycarbonate diol Ex. 1 — — 236 210099.6 99.7 pc-a Ex. 2 91 — 118 2100 99.2 99.5 pc-b Ex. 3 — 110 118 200099.3 99.5 pc-c Compara. — — 236 2000 96.3 98.7 pc-d Ex. 1 Compara. 91 —118 2100 96.5 98.6 pc-e Ex. 2 Compara. — 110 118 2000 96.0 98.3 pc-f Ex.3 Note) BDL, PDL and HDL mean 1,4-butanediol, 1,5-pentanediol and1,6-hexanediol, respectively.

COMPARATIVE EXAMPLE 4

A commercially available 1,5-pentanediol product which is different fromthat mentioned above in Comparative Examples 1 to 3 was purchased andanalyzed. The 1,5-pentanediol product had a purity of 98.9% by weightand contained 0.62% by weight of 1,5-hexanediol and 0.27% by weight of1,4-cyclohexanediol. Further, the 1,5-pentanediol product contained aplurality of unidentified impurities in a total amount of 0.21% byweight. Accordingly, the total content of diol monomers having primaryhydroxyl groups at both terminals thereof was 98.9% by weight, and thetotal content of diol monomers having a secondary hydroxyl group was0.89% by weight. A polycarbonate diol of 1,5-pentanediol was produced insubstantially the same manner as in Example 4 except that theabove-mentioned commercially available 1,5-pentanediol product was usedas a diol monomer. The produced polycarbonate diol was a white solidproduct at room temperature, and the number average molecular weightthereof was 1,800. The primary terminal OH ratio thereof was 96.5% andthe primary hydroxyl terminal purity thereof, as measured by a methodusing an alkali decomposition, was 98.9% by weight.

EXAMPLE 5

200 g of pc-a produced in Example 1 and 67.2 g of hexamethylenediisocyanate were charged into a reaction vessel equipped with astirrer, a thermometer and a refrigeration tube. A reaction of theresultant mixture was performed at 100° C. for 4 hours while stirring,thereby obtaining a urethane prepolymer having terminal NCO groups. Tothe obtained urethane prepolymer were added 30 g of 1,4-butanediol as achain extender and 0.006 g of dibutyltin dilaurylate as a catalyst. Theresultant mixture was reacted at 140° C. for 60 minutes in a universallaboratory scale extruder (Universal Laboratory Scale Extruder KR-35type; manufactured and sold by Kasamatsu Plastic Engineering andResearch Co., Ltd., Japan) equipped with a kneader, thereby obtaining athermoplastic polyurethane. The obtained thermoplastic polyurethane wasthen pelletized using the extruder. The number average molecular weight(Mn) and weight average molecular weight (Mw) of the thermoplasticpolyurethane were, respectively, 68,000 and 146,000 as measured by GPCanalysis, using a calibration curve obtained with respect to standardpolystyrene samples. The mechanical properties of the thermoplasticpolyurethane are shown in Table 2.

EXAMPLE 6

A thermoplastic polyurethane was produced in substantially the samemanner as in Example 5 except that the amounts of pc-a, hexamethylenediisocyanate and 1,4-butanediol were changed to 200 g, 24.5 g and 4.16g, respectively. The molecular weights and mechanical properties of thethermoplastic polyurethane are shown in Table 2.

EXAMPLES 7 AND 8

Thermoplastic polyurethanes were produced in substantially the samemanner as in Example 5 except that pc-b and pc-c were individually usedas a polycarbonate diol. The molecular weights and mechanical propertiesof the thermoplastic polyurethanes are shown in Table 2.

EXAMPLES 9 AND 10

Thermoplastic polyurethanes were produced in substantially the samemanner as in Example 6 except that pc-b and pc-c were individually usedas a polycarbonate diol. The molecular weights and mechanical propertiesof the thermoplastic polyurethanes are shown in Table 2.

TABLE 2 Properties of polyurethane Ex. 5 Ex. 6 Ex. 7 Ex. 8 Ex. 9 Ex. 10Polycarbonate diol pc-a pc-a pc-b pc-c pc-b pc-c Molecular weight numberaverage (Mn) 6.8 6.5 6.8 7.1 6.6 6.4 weight average. (Mw) 14.6 14.5 14.815.2 14.2 14.7 Mechanical properties MFR (g/10 min) 17 19 18 16 19 20Hardness (Shore D) 48 32 42 41 28 26 Tensile strength (MPa) 34 26 30 3125 26 Elongation (%) 660 700 730 760 760 790 Impact resilience (%) 38 4250 52 55 56 Brittleness temperature, −28 −30 −40 −42 −42 −44 t 100 (°C.)

COMPARATIVE EXAMPLES 5 TO 7

Thermoplastic polyurethanes were produced in substantially the samemanner as in Example 5 except that pc-d, pc-e and pc-f were individuallyused as a polycarbonate diol. The molecular weights and mechanicalproperties of the thermoplastic polyurethanes are shown in Table 3.

COMPARATIVE EXAMPLES 8 TO 10

Thermoplastic polyurethanes were produced in substantially the samemanner as in Example 6 except that pc-d, pc-e and pc-f were individuallyused as a polycarbonate diol. The molecular weights and mechanicalproperties of the thermoplastic polyurethanes are shown in Table 3.

TABLE 3 Com- Com- Com- Com- Com- Com- para. para. para. para. para.para. Properties of polyurethane Ex. 5 Ex. 6 Ex. 7 Ex. 8 Ex. 9 Ex. 10Polycarbonate diol pc-d pc-e pc-f pc-d pc-e pc-f Molecular weight numberaverage (Mn) 5.7 5.5 5.7 5.6 5.3 5.6 weight average. (Mw) 13.2 13.0 13.414.2 13.2 14.1 Mechanical properties MFR (g/10 min) 22 24 25 24 26 28Hardness (Shore D) 47 41 40 30 26 26 Tensile strength (MPa) 24 20 22 1815 16 Elongation (%) 450 580 620 460 620 640 Impact resilience (%) 33 4648 36 48 50 Brittleness temperature, −25 −35 −38 −28 −38 −40 t 100 (°C.)

EXAMPLE 11

200 g of pc-a produced in Example 1 and 67.2 g of hexamethylenediisocyanate were charged into a reaction vessel equipped with astirrer, a thermometer and a refrigeration tube. A reaction of theresultant mixture was performed at 100° C. for 4 hours while stirring,thereby obtaining a urethane prepolymer having terminal NCO groups. Tothe obtained urethane prepolymer were added 30 g of 1,4-butanediol as achain extender and 0.006 g of dibutyltin dilaurylate as a catalyst. Theresultant mixture was reacted at 140° C. for 180 minutes in a universallaboratory scale extruder (Universal Laboratory Scale Extruder KR-35type; manufactured and sold by Kasamatsu Plastic Engineering andResearch Co., Ltd., Japan) equipped with a kneader, thereby obtaining athermoplastic polyurethane. The obtained thermoplastic polyurethane wasthen pelletized using the extruder. The number average molecular weight(Mn) and weight average molecular weight (Mw) of the thermoplasticpolyurethane were, respectively, 78,000 and 175,000 as measured by GPCanalysis, using a calibration curve obtained with respect to standardpolystyrene samples. The mechanical properties of the thermoplasticpolyurethane are shown in Table 4.

EXAMPLES 12 AND 13

Thermoplastic polyurethanes were produced in substantially the samemanner as in Example 11 except that pc-b and pc-c were individually usedas a polycarbonate diol. The molecular weights and mechanical propertiesof the thermoplastic polyurethanes are shown in Table 4.

COMPARATIVE EXAMPLES 11 TO 13

Thermoplastic polyurethanes were produced in substantially the samemanner as in Example 11 except that pc-d, pc-e and pc-f wereindividually used as a polycarbonate diol. The molecular weights andmechanical properties of the thermoplastic polyurethanes are shown inTable 4.

TABLE 4 Com- Com- Com- Properties of Ex. Ex. Ex. para. para. para.Polyurethane 11 12 13 Ex. 11 Ex. 12 Ex. 13 Polycarbonate diol pc-a pc-bpc-c pc-d pc-e pc-f Molecular weight number average (Mn) 7.8 7.5 7.7 6.56.4 6.6 weight average (Mw) 17.5 17.3 17.7 15.8 15.5 16.3 Mechanicalproperties MFR (g/10 min) 5.4 5.5 5.7 12 14 14 Hardness (Shore D) 48 4241 48 42 40 Tensile strength (MPa) 38 33 35 26 24 25 Elongation (%) 690750 790 500 620 630 Impact resilience (%) 40 52 54 35 46 48 Brittlenesstempera- −26 −41 −42 −24 −34 −39 ture, t 100 (° C.)

INDUSTRIAL APPLICABILITY

The polycarbonate diol of the present invention exhibits highpolymerization activity in a polyurethane-forming reaction and apolyester-forming reaction. Therefore, when the polycarbonate diol ofthe present invention is used for producing a thermoplasticpolyurethane, a poly ester elastomer and the like, the desiredpolymerization reactions can proceed at high rate, as compared to thecase of the use of the conventional polycarbonate diol. Further, thethermoplastic polyurethane of the present invention has remarkablyexcellent properties with respect to strength, elongation, impactresilience and low temperature properties and hence can beadvantageously used in various application fields, such as the fields ofautomobile parts, parts for household electric appliances, toys andmiscellaneous goods. Since the thermoplastic polyurethane of the presentinvention exhibits especially improved mechanical strength, thethermoplastic polyurethane can be advantageously used in applicationfields requiring high durability, such as the fields of industrialparts, e.g., hoses, rollers and boots. The thermoplastic polyurethane isalso advantageous for use as a material for interior and exterior partsfor an automobile, such as a window mole, a bumper, a skin part for aninstrument panel and grips; wrist bands for watches and shoe soles.

1. A polycarbonate diol comprising recurring units each independentlyrepresented by the following formula (1):

wherein R represents a divalent aliphatic or alicyclic hydrocarbon grouphaving 2 to 10 carbon atoms, and terminal hydroxyl groups, wherein 50 to100% by mole of said recurring units of formula (1) are eachindependently represented by the following formula (2):

wherein n is 5 or 6, and wherein: when the amount of recurring units offormula (2) wherein n=5 is from 50 to 100% by mole, based on the totalmolar amount of said recurring units of formula (1), said polycarbonatediol has a primary terminal OH ratio of 97% or more, and when the amountof recurring units of formula (2) wherein n=5 is from 0 to less than 50%by mole, based on the total molar amount of said recurring units offormula (1), said polycarbonate diol has a primary terminal OH ratio of99% or more, said primary terminal OH ratio being defined as the weightpercentage of diol monomers having primary hydroxyl groups at bothterminals thereof, based on the total weight of the alcohols inclusiveof diol monomers, wherein said alcohols, inclusive of diol monomers, arederived from the terminal diol segments of said polycarbonate diol andare contained in a fraction obtained by heating said polycarbonate diolat a temperature of from 160 to 200° C. under a pressure of 0.4 kPa orless while stirring.
 2. A polycarbonate diol according to claim 1,wherein, when said polycarbonate diol is decomposed with an alkali toobtain a mixture of diol monomers corresponding to all of the diolsegments of said polycarbonate diol, said mixture of diol monomersexhibits: a primary hydroxyl terminal purity of 99.0% by weight or morewhen, in said polycarbonate diol, the amount of recurring units offormula (2) wherein n=5 is from 50 to 100% by mole, based on the totalmolar amount of said recurring units of formula (1), and a primaryhydroxyl terminal purity of 99.5% by weight or more when, in saidpolycarbonate diol, the amount of recurring units of formula (2) whereinn=5 is from 0 to less than 50% by mole, based on the total molar amountof said recurring units of formula (1), said primary hydroxyl terminalpurity being defined as the weight percentage of the diol monomershaving primary hydroxyl groups at both terminals thereof, based on theweight of said mixture of diol monomers.
 3. A thermoplastic polyurethaneobtained by copolymerizing the polycarbonate diol of claim 1 or 2 and apolyisocyanate.